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I've picked up a pair of secondhand Sanyo micro hi-fi speakers (rated 6W, 4 ohms impedance) and I'm looking to build a simple bluetooth audio set-up using a preassembled bluetooth digital amplifier (link).

The amplifier board runs from a 5V micro USB power source and, according to the specifications, expects 2x3W speakers at 4-8 ohms.

As there is a mismatched power, I'm trying to work out what would happen if I just connected them as is. Would there be:

1) The speakers will only output a low volume

2) The speakers will go to full volume, but the sound will be very distorted.

3) Something else??

Based on research, I think that option 1 would be the outcome - am I right? If so, the volume produced may in fact be ok - the speaker will be needed for a 4m x 5m room for occasional use at modest volumes. Is this realistic?

Happy to receive any other suggestions for an alternative amplifier board, or if it could be easily modified.

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  • \$\begingroup\$ The \$4\:\Omega\$ specification for your speakers fits the specification you provided for the amplifier. Your speakers are specified to operate at a higher power, which merely means than can handle more power than the amplifier can dish out. Which is fine, as well. So they should simply work fine, without any problems, to the limit of the capacity of your amplifier. \$\endgroup\$ – jonk Apr 7 '17 at 0:15
  • \$\begingroup\$ There is no mismatch. The amplifier outputs 3+3 W and the speakers have a maximum rated power of 6 W. They will be fine together. Obviously you will only get sound levels that correspond to 3+3 W out of the speakers. \$\endgroup\$ – Jack Creasey Apr 7 '17 at 0:16
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The power rating of a speaker indicates the maximum power it can accept without damage. A speaker of an equal or higher power rating than the amplifier is a good idea, otherwise the amplifier at maximum volume is likely to damage the speakers.

The volume will depend on the sensitivity of the speakers. Although sensitivity varies between speakers of different construction, sensitivity is not directly related to a speaker's power rating. Meaning, a 3W speaker will not necessarily sound "louder" than a 6W speaker connected to the same amplifier. There's no particular reason to look for a 3W speaker unless you are trying to cut costs.

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